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gcse Chemistry > Products From Crude Oil > Flashcards

Products From Crude Oil Flashcards

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1
Q

What are alkenes

A

Another family of hydrocarbons that contain a carbon carbon double bond

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2
Q

What do double bond involve

A

Sharing two pairs of electrons

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3
Q

What does unsaturated mean

A

Contains at least one double bond

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4
Q

What is the general formula for alkenes

A

C(n)H(2n)

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5
Q

Why is there not a methene

A

There is only one carbon atom is methane. There needs to be a carbon carbon double bond for for there to be an alkene

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6
Q

How many bonds does carbon need to make to get a full outer shell

A

4

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7
Q

What can alkenes also undergo just like alkanes

A

Combustion

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8
Q

What is cracking

A

A process which breaks down large hydrocarbon molecules into smaller, more useful molecules

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9
Q

Why do we need to crack

A

Some of the heavier fractions from fractional distillation are not useful as they are made of large molecules and are poor fuels

The smaller hydrocarbons are more useful

Unfortunately there is a high supply and low demand for large hydrocarbons and a low supply and a high demand for small hydrocarbons

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10
Q

How does cracking work

A

It involves heating the hydrocarbon strongly so it turns into a gas and passes through a hot catalyst

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11
Q

What type of reaction is cracking and what does it mean

A

Thermal decomposition reaction - breaking down a substance using heat

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12
Q

What are the two types of products from cracking

A

Smaller alkane that is a more useful fuel

Alkenes

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13
Q

What is the test for alkenes and result and explanation

A

Bromine water (orange)

Alkene present - turns colourless
Alkane present - stays orange

Explanation - alkenes have double bond so reacts as the double bond breaks

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14
Q

Monomer definition

A

A small molecule that can combine wth similar molecules to form a long molecule called a polymer

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15
Q

Polymer definition

A

Very long molecules made of smaller molecules called monomer

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16
Q

What is addition polymerisation

A

The process where monomers join together by single bonds to form 1 large polymer molecule

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17
Q

What is an example of a monomer

A

Alkenes

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18
Q

What happens during addition polymerisation

A

Under high pressures and temperatures double bonds in the monomer molecules break to form a single bond

Millions of monomers join together by single bonds to form one long polymer

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19
Q

What is the use of polyethene and what is the displayed formula

A

Plastic bags, milk cartons, shampoo bottles

n C=C

[—–C-C—– ] n

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20
Q

What is the use of polypropene

A

Rope, milk crates

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21
Q

Why does polystyrene and polypropene have different properties

A

They are made from different polymers and before that monomer so have different properties

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22
Q

What are the two types of polyethene

A

Low density and high density

23
Q

How is low density polyethene made

A

Under high pressures and a trace of oxygen

24
Q

Why is low density polyethene low density

A

The polymer chains have random branches so are unable to patch closely together

25
Q

How is high density polyethene formed

A

Using a catalyst at 50degreesC, slightly high pressure

26
Q

Why is high density polyethene high density

A

The polymer chains are straighter and without branches so are able to pack closely together

27
Q

Why do plastics soften easily when heated

A

There are weak intermolecular forces between the molecules as there are no covalent bonds (cross links) so the plastic can soften easily when heated

28
Q

How can we classify polymers

A

By looking at what happens when they get heated

29
Q

What are thermosoftening polymers

A

Polymers which soften easily when heated and reset when cooled. They are made of polymer chains that are tangled together and can easily separate as they have weak intermolecular forces between them

30
Q

What are thermosetting polymers

A

Polymers that do not melt when heated a they have strong covalent bonds between. The polymer chains called cross links

31
Q

Properties of thermosetting polymers (2)

A

Cross links don’t break when heated

Rigid

32
Q

Properties of thermosoftening polymers

A

Weak intermolecular forces that break when heated

Melts easily but rehardened again when cooled so can be remoulded

33
Q

Why are plastic bags made out of thermosoftening polymers (2)

A

Flexible

Tensile strength (can stretch)

34
Q

Why are thermosetting polymers used for pan handles

A

Don’t melt under intense heat during cooking

Rigid

35
Q

Why are waste plastics a problem

A

They take up space in landfill sites and take a long time to break down. Wildlife might also get trapped in the waste plastic and die

36
Q

What are biodegradable polymers

A

These plastics rot away in soil and are broken down by microorganisms

37
Q

What raw material is good to make biodegradable stuff

A

Plant

38
Q

What is the monomer of polylacticacid

A

Lactic acid

39
Q

How can non-biodegradable polymers be made to decompose more quickly

A

Use fermented cornstarch to make plastic material

40
Q

What are the problems with using cornstarch to make polymers (2)

A

Crops for food are being used for plastics (famine + increases food prices)

Destruction of habitats

41
Q

What is the problem with using degradable polymers that break down in light

A

Most of the plastics won’t decompose as they are buried in the landfill site

42
Q

What does corn starch speed up decomposition

A

Microorganisms feed on the corn starch in the plastic

43
Q

What are the two processes for making ethanol

A

Fermentation of sugar

Hydration of ethene

44
Q

Advantages of using the method fermentation of sugar to produce ethanol (3)

A

Uses renewable plant material
Carbon neutral
Cheap conditions- anaerobic respiration in yeast and warm temperatures

45
Q

Advantages of using the method of hydration of ethene to produce ethanol (4)

A

Continuous process
Fast reaction
100% pure product first time
High yield

46
Q

Disadvantages for using fermentation of sugar for producing ethanol (5)

A 
Slow reaction
Batch process
Not 100% pure product first time
Low yield
Uses land to grow sugar cane (famine + increase food prices)
47
Q

Disadvantages for using hydration of ethene for producing ethanol (3)

A

Uses finite fossil fuels
Not carbon neutral
High temperatures and pressures

48
Q

How is the chemical structure of an alkene different to an alkane

A

Alkenes have double bonds

49
Q

What needs to reacts with ethene to produce ethanol

A

Steam

50
Q

Two differences between cracking and polymerisation

A

Long chains turn to short chains in cracking and short monomers join to make a long polymer

Cracking had more than one product whereas polymerisation has one

51
Q

Why is cracking an important process in the oil industry

A

The supply for shorter hydrocarbon chains is low but the demand is high. The supply for longer hydrocarbon chains is high but the demand is low. Cracking will satisfy the demand

52
Q

What is the process called that separates a mixture with different boiling points

A

Fractional distillation

53
Q

Why is it important to keep control variables constant

A

So that only the independent variable ins allowed to have an affect on the dependent variable

gcse Chemistry (8 decks)

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